A next-generation energy supply system called smart grid is a mechanism to realize more stable supply of power while attempting to effectively use renewable energy by controlling demand and supply balance of power using information network technologies. Since power generation utilizing renewable energy such as solar power generation and wind power generation has large power fluctuation due to meteorological conditions, it is required to control demand and supply for accommodating the power fluctuation by other controllable power supplies, batteries or adjusting power demand. A technology called demand, response is known as an approach in demand of such control on demand and supply.
The demand response is to limit power use at the user side on the basis of requests from utility companies for the purposes of curbing peak demand when energy demands rise, load leveling by shifting demands to light-load periods, and suppressing short-term fluctuation when a great deal of renewable energy is introduced. Various methods can be considered for realizing the demand response. Examples thereof include a method of collecting information on power use schedules of users under electricity supply contracts by a server managed by a utility company, estimating the total amount of power consumption assumed in the future to make adjustments to meet the purpose of the demand response described above, and requesting some users to change the power use schedules.
If the information collected by the server is stolen without authorization when the demand response is realized in such a method, the life pattern or the like of a user can be inferred from the information, which leads to privacy invasion.